transfer box chain

[davey]

i think i need to replace the transfer box chain on my 04, 3.o x3 auto, the usual clunks, is it possible to replace the chain with the box in place, to undo the rear prop, and pull the front case off, it looks possible????????. rgds dave

[kkx5]

...... You got new chain in your transfer...

[davey]

started clunking as it chenges up thro 1st and second, sounds coming from trans box, ok when cruising, puzzled, !!

[stevox5]

What tyres have you got fitted and what tread depths?
These are very very sensitive with tyres , if you have non approved (star rated ) tyres fitted they tend to wind the transfer box up and clunk line hell at low speed especially when changing from first to second gear.

[davey]

i,ll check the tyre sizes tomorrow, they not run flat, rgds davey

[kkx5]

[quote="davey"]
started clunking as it chenges up thro 1st and second, sounds coming from trans box, ok when cruising, puzzled, !!
[/quote]
Transfer is as new. You got new chain, new bearings, new seals on it. Search elsewhere. X3 are prone for rear prop shaft double joint failure (that one close to rear diff)...and the sound is, like, coming from transfer...

[davey]

great, thanks for that, i,ll check that as soon as it stops raining, lol, rgds davey,

[davey]

also, i got 235...55..18s on the front, and 255..55..18s on the back, should that make a difference??. rgds davey

[X5Sport]

That profile seems wrong. Are you sure that both axles are /55 even with different widths?  Should be something like /55 on the front and /50 on the rear for those widths, or both sets completely identical.  The factory sizes for 18" wheels are shown as 255/55 R18 all round, not as you state.

If they are different sizes but both /55 profile all around then you are asking for trouble due to the different rolling radius causing transmission wind-up.  That will upset the transfer box and cause the noises you have.

Richard

[jagr]

[quote="davey"]
also, i got 235...55..18s on the front, and 255..55..18s on the back, should that make a difference??. rgds davey
[/quote]

None of those are the correct size tyres so would assume they are not 'star' marked.

If you have the staggered setup it should be:

235/50/18 Front
255/45/18 Rear

If standard 18" they should be 235/50/18 all round.

[davey]

so get 255...55..18s for the backs, and make all the same???

[davey]

ok, i double checked, 255..45..r18.rear, ....... 235..50..r18. front,  ??

[jagr]

[quote="davey"]
so get 255...55..18s for the backs, and make all the same???
[/quote]

I wouldn't as they would still be wrong
What make are your tyres? Do they have a 'Star' mark on them like this

[davey]

the backs, 255.45.18 michelins, the fronts 235.50.18 khomos, no stars, rgds davey

[jagr]

[quote="davey"]
the backs, 255.45.18 michelins, the fronts 235.50.18 khomos, no stars, rgds davey
[/quote]

The choice is yours but I would change all tyres to 'Star' marked tyres.
When I had the 18" staggered setup I had Dunlop SP01 tyres which were BMW original fitments.